Stabilization of nitroform salts



United States Patent Ofitice 3,378,595 Patented Apr. 16, 1968 3,378,595 STABILIZATION F NITROFORM SALTS John A. Brown, Berkeley Heights, and John R. Lovett,

Edison, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Feb. 27, 1961, Ser. No. 92,088 6 Claims. (Cl. 260-644) This invention relates to the stabilization of hydrazine nitroform and of other amine salts of nitroforrn by adat 90 C.

TABLE.S'IABILIZATION OF HNF BY ACIDS AT 90 C.

Specimen hrs. hrs. hrs. hrs. hrs. hrs. hrs.

(Untreated HNF)- 0 2 7 21 1% P20 0 0 0 1 1 8 1% HSPOJ 0 0 0 1 1 10 1% Oxalic Ac 0 0 0 0 0 1 3 2% Pieric Acid. 0 0 0 2 3 14 Decomposition, cc. Gas/Gram at STP in mixture of a small amount of an acid, such as oxalic acid, picric acid, phosphorous acid, phosphoric acid, excess nitroform acid, and phosphorous pentoxide, etc.

A number of salts of nitroform, HC(NO have been considered as valuable high energy ingredients in rocket propellant formulations. Among these salts, hydrazine nitroform, N H -HC(NO guanidine nitroform and certain other amine nitroform salts, particularly of polyalkyleneamines, have superior thermal stability relative to other nitroform salts, but additional stabilization is desirable.

Experience in preparing hydrazine nitroform (HNF) indicates that the ratio of the reactants hydrazine and nitroform, the purity of the nitroform and the diluent may have a bearing on stability of the product. More stable products were obtained with an excess of freshly purified (water-white) nitroform. Anhydrous methanol makes a good reaction medium.

In making stability tests on the nitroform salts, it has been noted that the rate of decomposition, which can be measured by the gas evolved during a period of time, depends on the temperature. Between 60 C. and C., the increased rate of gas evolution is not very great. At C. the rate is very much increased, and in fact, appears to go from a linear rate to an autocatalytic parabolic rate.

The results of various tests indicate that decomposition products, such as free hydrazine, may catalyze the decomposition.

In accordance with the present invention, a number of acid additives have been found to be strikingly effective for stabilizing the nitroform salts of amines, such as hydrazine nitroform. These additives are eifective even in small amounts, e.g. about 1 to 5 wt. percent.

In the table the signs indicate a high rate of decomposition, above 50 cc. per gram, the gas being determined as under standard conditions of temperature andpressure (STP).

While there are d-ifierences in the effectiveness of the acidic additives, which may involve other properties of the additives, such as reducing action, it has been found that improved stability is obtainable with all acids tested. Other acids which are indicated to be suitable as stabilizing additives are acids such as dichloracetic, maleic, benzoic, salicylic, tartaric, acetic, sulfuric, and the like.

The acid additives are useful for stabilizing the amide nitroform salts during storage, handling and preparation of rocket fuel propellant systems. The nitroform salts stabilized by a small amount of additive are useful as potent oxygen oxidizers. The polymeric nitroform salts, e.g. polyalkyleneamine nitroformates, can be used as high-energy binders. The nitroform salts can be used as oxidizers, with powdered metals, e.g., Al, Be, B, Mg, and Li with various binders and other kinds of oxidizers, hexanitroethane, tetrakis (N1 butane), tetrakis (NF; furan) etc.

What is claimed is:

1. Hydrazine nitroform stabilized by about 1 to 5 wt. percent of an admixed compound selected from the group consisting of P 0 H PO oxalic acid, picric acid, and nitroform.

2. Hydrazine nitroform stabilized by about 1 to 5 wt. percent of excess nitroform.

3. A hydrazine nitroform stabilized by about 1 to 5 wt. percent of admixed P 0 4. Hydrazine nitroform stabilized by about 1 to 5 Wt. percent of admixed H PO 5. Hydrazine nitroform stabilized by about 1 to 5 wt. percent of admixed oxalic acid.

6. Hydrazine nitroform stabilized by about 1 to 5 wt. percent of admixed picric acid.

References Cited UNITED STATES PATENTS 3,140,317 7/1964 Groves 260-644 3,213,609 10/1965 Johnston et al 14936 X 3,297,747 1/1967 Thornton 260644 X CARL D. QUARFORTH, Primary Examiner. LEON D. ROSDOL, Examiner.

J. w. WHISLER, L. A. SEBASTIAN,

Assistant Examiners. 

1. HYDRAZINE NITROFORM STABILIZED BY ABOUT 1 TO 5 WT. PERCENT OF AN ADMIXED COMPOUND SELECTED FROM THE GROUP CONSISTING OF P2O5, H3PO4, OXALIC ACID, PICRIC ACID, AND NITROFORM. 